Conventionally, image processing apparatuses have been known for processing an image of a mixed type of a line image region and an halftone image region by identifying a line image region and a halftone image region based on a feature amount of the image in a vicinity of a target pixel to be processed to process the image in the line image region in a different manner from the image in the halftone region.
The described image processing apparatuses are disclosed in, for example, Japanese Unexamined Patent Publication No 137378/1989 (Tokukaihei 1-137378) which includes space filtering devices for space-filtering an image input in which a line image region and a tone image region are mixed; binarization devices for binarizing an output from the space filtering device, wherein a feature amount of an image in a vicinity of a target pixel to be processed is extracted so as to switch the space filtering device and the binarizing device based on the feature amount as being extracted, and the space filtering device and the binarizing device are switched based on the feature amount as extracted. Furthermore, according to the image processing device of the described publication, as shown in FIG. 1, of the described publication the device for binarizing the feature amount extraction data is switched to a multiplexer provided in a pre-stage.
However, the described image processing device does not take the variable magnification process of resolution conversion into consideration both in the device for extracting the feature amount and the device for altering the binarizing device based on the result of extraction of the feature amount. Namely, the image processing device is arranged so as to perform a predetermined image process irrespectively of the magnification factor or the resolution conversion factor.
Furthermore, the image processing apparatus cannot be applied to the processing of the image after the magnification process or the resolution conversion as the apparatus is not provided with a circuit for carrying out a magnification process or a resolution conversion process of feature extraction data. Therefore, in the described image processing apparatus, segmentation of the image data processed with the magnification process or the resolution conversion cannot be performed with high precision in consideration of the magnification factor or the resolution conversion factor. For the above reasons, the image processing apparatus has a drawback in that the filtering process of the binairizing process after the magnification or the resolution conversion are lowered, which causes a degrading of a quality of the resulting processed image.